Sounds like the infamous SVB, aka, Squash Vine Borer. It's a moth that lays a bunch of little brown eggs..like the size of a pinhead.They lay the eggs at multiple places, one or two at a time. They hatch, burrow into the squash, and maggot their way through, eat their way out, pupate in the ground, and come out, and start the evil cycle all over again.
I did a Google search and they said you can wrap the young stems with foil to keep the buggers at bay. Will try that on some of the plants to see how that works.
That may be right, but I didn’t think it would kill a plant in one day. What ever it was, it only took 24 hours to got from a healthy plant to dead.